Previous work has shown that chitin synthetases 1, 2 and 3 have distinct functions in septum formation and cell separation in yeast. By carrying out several in-frame deletions, it has been established that an amino terminal portion of chitin synthetase 2 (Chs2) is not essential for activity or function. This is also probably true of the corresponding region of chitin synthetase 1 (Chs1). Experiments on the turnover of Chs1, Chs2 and Chs3 activity and of the corresponding messenger RNA's after shutting off transcription indicate that in vivo regulation of these enzymes probably occurs at the post-translation level. Synthesis of the major structural polysaccharide of the yeast cell wall, beta(1->3) glucan, is catalyzed by a membrane-bound system. By extraction with salts and detergents two fractions, A and B, have been solubilized that are needed, in combination with GTP, for glucan synthetase activity. Results with partially purified fraction A (the GTP-binding component) indicate that it may contain an intrinsic GTPase, whose modulation may be important for the control of glucan synthetase activity and of cell wall growth.